P0440

Trying to narrow down a p0440 code that is always set just as I start the vehichle. Checked gas cap. I don't have much money or time in a garage to troubleshoot, so hoping someone here can narrow down the cause before sunday since it happens religiously after a cold start.

440 code covers a lot of things.
You will need a scanner to get the other evap codes to help narrow it down.
Like small leak or large leak or what solenoid or sensor is not working.
First thing to check for is gas tank holding vacuum.
Check your vacuum and vent lines from engine back to fuel tank.
The get the good engine capable codes and post back code. no

K, I'm a schmuck. I'd been clearing the code all week without checking it until I got a new gas cap, when I discovered the code switched sometime to P0147. The original P0440 was probably thrown from a new brand of gas (I've heard that can happen) or a loose cap, and the wet cold weather since has been setting the O2 sensor code. Ah well, at least I got a new locking gas cap out of the deal. Now I can annoy the neighbours without fear of sugar in tank retaliation. :wink: Maybe I'll switch out the sensor for one of the old ones I removed that were working fine and hope they go on sale soon.

Thanks for the help. For future reference, would a P0440 usually accompany other evap codes?

...For future reference, would a P0440 usually accompany other evap codes?


It can be accompanied by one or more of the following DTC's: P0442, P0446, P0452, P0453, P0461, P0462, P0463 and P1441. Or it may just pop up alone. As MT said, the evap system is one of the most difficult to troubleshoot.